Apparatus and method for sputter depositing dielectric films on a substrate

Abstract

Apparatus and method for sputter depositing a layer of material comprises a sputtering chamber having an internal conductive wall which provides an electrical reference for plasma during sputter deposition. A conductive shield positioned in the processing space of the chamber between the target and the substrate is configured for capturing sputtered material which would deposit on the chamber wall surface during sputter deposition. The conductive shield reduces the amount of sputtered material depositing on the chamber wall and maintains a surface portion of the wall as a generally stable electrical reference for the plasma and is further operable for passing plasma therethrough during deposition to contact the stable electrical reference.

What is claimed is:  
     
       1. An apparatus for sputter depositing a layer of material on a substrate comprising: 
       a sputtering chamber having an internal conductive wall which defines a processing space;  
       a substrate mount positioned in the processing space for supporting a substrate therein;  
       a sputter target mount positioned in the processing space for supporting a target therein opposite said substrate mount;  
       a power source for biasing a target and exciting a process gas introduced in the processing space into a plasma such that the plasma will sputter material from a target supported on said target mount and the sputtered material will deposit on a substrate supported on said substrate mount and on a surface of the chamber wall to form respective material layers thereon, a surface of the internal chamber wall operable for providing an electrical reference for the plasma during sputter deposition;  
       a conductive shield positioned in the processing space between the target mount and the substrate mount and configured for capturing a portion of the sputtered material which would otherwise deposit on the chamber wall surface during sputter deposition;  
       a source of ground potential, the conductive shield being coupled to the source of ground potential for grounding the shield during sputter deposition;  
       the conductive shield operable for reducing the amount of sputtered material which will deposit on a portion of the chamber wall surface and maintaining said chamber wall surface portion as a generally stable electrical reference for the plasma, and further including a plurality of apertures formed therein, the apertures comprising a cumulative area in the range of approximately 10% to 50% of the area of an inner surface of the shield for being operable for passing plasma therethrough during sputter deposition to contact said stable electrical reference;  
       at least one of the shield apertures having at least one dimension in the range of approximately 0.25 to 2.0 times the mean free path length of a process gas to be introduced into the chamber;  
       whereby a stable and continuous sputter deposition process may be achieved.  
     
     
       2. The apparatus of  claim 1  wherein the shield has a surface and is operable to reduce sputter deposition on said shield surface for providing another generally stable electrical reference for the plasma passing through the shield during sputter deposition. 
     
     
       3. The apparatus of  claim 1  wherein the chamber wall is coupleable to an electrical ground potential, the apparatus further comprising a source of ground potential for coupling to the wall to ground said wall during a sputter deposition process. 
     
     
       4. The apparatus of  claim 1  wherein the chamber and conductive internal wall are electrically coupled together for being maintained at a generally equal electrical potential during a sputter deposition process. 
     
     
       5. The apparatus of  claim 1  wherein the apertures are in the shape of geometric figures. 
     
     
       6. The apparatus of  claim 5  wherein the apertures are in the shape of circles. 
     
     
       7. The apparatus of  claim 5  wherein the apertures are in the shape of rectangles. 
     
     
       8. An apparatus for sputter depositing a layer of material on a substrate comprising: 
       a sputtering chamber having an internal conductive wall which defines a processing space;  
       a substrate mount positioned in the processing space for supporting a substrate therein;  
       a sputter target positioned in the processing space opposite said substrate mount;  
       a power source for biasing the target and exciting a process gas introduced in the processing space into a plasma such that the plasma sputters material from the target and the sputter material deposits on a substrate supported on said substrate mount and on a surface of the chamber wall to form respective material layers thereon, a surface of the chamber wall operable for providing an electrical reference for the plasma during sputter deposition;  
       a conductive shield positioned in the processing space between the target mount and the substrate mount and configured for capturing a portion of the sputtered material which would otherwise deposit on the chamber wall surface during sputter deposition, the shield having a surface operable for providing another electrical reference for the plasma;  
       a source of ground potential coupled to the conductive shield and chamber wall for maintaining said shield and wall as a ground reference;  
       the conductive shield operable for reducing the amount of sputtered material which deposits on a portion of the chamber wall surface and maintaining said chamber wall surface portion as a generally stable ground reference for the plasma, and further including a plurality of apertures formed therein, the apertures comprising a cumulative area in the range of approximately 10% to 50% of the area of an inner surface of the shield for being operable for passing plasma therethrough during sputter deposition to contact said shield and wall ground references;  
       at least one of the shield apertures having at least one dimension in the range of approximately 0.25 to 2.0 times the mean free path length of a process gas to be introduced into the chamber;  
       whereby a stable and continuous sputter deposition process may be achieved.  
     
     
       9. The apparatus of  claim 8  wherein the shield is operable to reduce sputter deposition on said shield electrical reference surface for providing another generally stable ground reference for the plasma passing through the shield during sputter deposition. 
     
     
       10. The apparatus of  claim 8  wherein the apertures are in the shape of geometric figures. 
     
     
       11. A method for sputter depositing a layer of material on a substrate comprising: 
       providing a sputtering chamber having an internal conductive wall which defines a processing space;  
       positioning a substrate in the processing space;  
       positioning a sputter target in the processing space opposite said substrate;  
       biasing the target and exciting a process gas introduced in the processing space into a plasma such that the plasma sputters material from the target and the sputter material deposits on the substrate and on the chamber wall to form respective material layers thereon, a surface of the chamber wall providing an electrical reference for the plasma during sputter deposition;  
       positioning a conductive shield between the target and substrate for capturing an amount of the sputtered material to reduce the amount of sputtered material which otherwise deposits on a portion of the chamber wall surface and maintaining said chamber wall surface portion as a generally stable electrical reference for the plasma;  
       the shield including a plurality of apertures comprising a cumulative area in the range of approximately 10% to 50% of the area of an inner surface of the shield;  
       the process gas having particles with a predetermined mean free path length and at least one of the shield apertures having at least one dimension in the range of approximately 0.25 to 2.0 times the mean free path length of a process gas introduced into the chamber;  
       passing plasma through the apertures and to the stable electrical reference for maintaining a stable plasma;  
       coupling the conductive shield to a source of ground potential for grounding the shield during sputter deposition;  
       whereby a stable and continuous sputter deposition process may be achieved.  
     
     
       12. The method of  claim 11  further comprising capturing an amount of the sputtered material with an inner surface of the conductive shield positioned between the target and substrate. 
     
     
       13. The method of  claim 11  further comprising coupling a source of ground potential to the chamber to ground said chamber wall surface during a sputter deposition process for providing a stable ground reference for the plasma. 
     
     
       14. The method of  claim 11  further comprising coupling together the conductive shield and conductive chamber wall and maintaining the surfaces of the wall and shield at an electrical potential during a sputter deposition process to provide said electrical reference.